Question

when i arrived at her house she (watching) a film on television​

Answer 1

$\bf\underline{Filling \:blank :-}$

When I arrived at her house she $\bf\underline{was \:watching}$ a film on television.



$\bf\underline{Additional \:Information :-}$

▪The sentence given above in the question is in past tense.

▪"Watching" comes in $\bf {Past \:Continuous \:Tense}$ so in this tense helping verbs are $\bf {was/were}$

▪"Was" is for singular and "were" is for plural.

___________________________ _ _

Answer 2

When I arrived at her house she $\bf\underline{was \:watching}$ a film on television.